Есть и другие схемы, основанные на представлении цвета не как смеси базовых цветов, а функции параметров иного рода. Например, довольно популярна схема HSB, в которой параметрами являются оттенок (Hue), насыщенность (Saturation), и яркость (Lightness).

>>C = (G + B)/2
>>M = (R + B)/2
>>Y = (R + G)/2

A>Но я вполне готов признать, что Я и все разработчики ICM, вместе не правы, если вам так лучше спится.

    // Трансформировать белый RGB в CMYK
    source.rgb.red = 255;
    source.rgb.green = 255;
    source.rgb.blue = 255;

        printf( 
        "\t\tRGB(255, 255, 255) aka 'White' corresponds to CMYK(%3d, %3d, %3d, %3d)\n",
                ( BYTE ) destination.cmyk.cyan,
                ( BYTE ) destination.cmyk.magenta,
                ( BYTE ) destination.cmyk.yellow,
                ( BYTE ) destination.cmyk.black );

From: Antti Nivala (antti.nivala@motivesys.com)
Subject: Re: Transforming colors with ICM 
Date: 2004-01-06 05:04:42 PST 

> > Doesn't anybody have any clue about this? It can't be that I'm the only
> > one experiencing this problem, am I?

I think I had the same problem, too. I first assumed I can just use ICM to
convert from CMYK to RGB using TranslateColors. However, this only works if
the color transformation you give to TranslateColors is compatible with the
color spaces involved.

To convert from CMYK to RGB using TranslateColors, you must have a color
transform that converts from a CMYK-based ICC profile's color space to an
RGB-based profile's color space. If you just take the printer's profile and
use it as the source you might likely have an RGB profile because
non-PostScript Windows printers can only have RGB profiles. Only PostScript
printers can have CMYK profiles in Windows.

What I found most strange was that if I use TranslateColors to convert from
CMYK to RGB and give it an RGB-RGB transformation, it claims success but
does not really do the conversion. I think it just copied the values
literally and reported success (why???). This could explain why your CMYK
yellow (0, 0, 65535, 0) results in RGB blue (0, 0, 65535): TranslateColors
did not really do any conversion, and you are interpreting the original CMYK
values as if they were RGB (yellow and blue are in the same byte slots in
the union...).

TranslateBitmapBits reports an error in a similar situation, I don't
understand why TranslateColors does not.

Antti Nivala
Motive Systems

    ENUMTYPE enumtype;
    ZeroMemory(&enumtype, sizeof(ENUMTYPE));
    enumtype.dwSize = sizeof(ENUMTYPE);
    enumtype.dwVersion = ENUM_TYPE_VERSION;
    enumtype.dwFields = ET_DATACOLORSPACE;
    enumtype.dwDataColorSpace = SPACE_CMYK;

    char buf[10000];
    DWORD dwSize = sizeof(buf), dwCount = 0;
    if (EnumColorProfiles(NULL, &enumtype, (PBYTE)buf, &dwSize, &dwCount)) {
        char *tmp = buf;
        for (DWORD i = 0; i < dwCount; i ++) {
            printf("%s\n", tmp);
            tmp += strlen(tmp) + 1;
        }
    }

        Testing profile 'Photoshop4DefaultCMYK.icc'
                RGB(FFFF, FFFF, FFFF) aka 'White' corresponds to CMYK(  10,    A,    0,    0)
                RGB(FFFF,    0,    0) aka 'Red'   corresponds to CMYK(   0, EB3C, FF5C,    0)
                RGB(   0, FFFF,    0) aka 'Green' corresponds to CMYK(A5D1,    0, EE2A,    0)
                RGB(   0,    0, FFFF) aka 'Blue'  corresponds to CMYK(FFFF, DABE,    0,    0)

A>>Но я вполне готов признать, что Я и все разработчики ICM, вместе не правы, если вам так лучше спится.

DISPLAY ADAPTERS
        Enumerating for adapter '\\.\DISPLAY1'
        Testing profile 'C:\WINDOWS\system32\spool\DRIVERS\COLOR\995E.ICM'
                RGB(65535, 65535, 65535) aka 'White' corresponds to CMYK(255,  40, 248, 204)
                RGB(65535,   0,   0) aka 'Red'   corresponds to CMYK(255,   0,   0, 204)
                RGB(  0, 65535,   0) aka 'Green' corresponds to CMYK( 21, 105,   0, 204)
                RGB(  0,   0, 65535) aka 'Blue'  corresponds to CMYK(  9, 168,  74, 204)
        End of enumeration for adapter '\\.\DISPLAY1'
        Enumerating for adapter '\\.\DISPLAYV1'
        End of enumeration for adapter '\\.\DISPLAYV1'
        Enumerating for adapter '\\.\DISPLAYV2'
        End of enumeration for adapter '\\.\DISPLAYV2'
END DISPLAY ADAPTERS

PRINTERS
        Enumerating for printer 'PDFConverter'
        End of enumeration for printer 'PDFConverter'
        Enumerating for printer 'PDF Creator'
        End of enumeration for printer 'PDF Creator'
        Enumerating for printer 'Fax'
        End of enumeration for printer 'Fax'
END PRINTERS

struct CMYKCOLOR {
  WORD    cyan;
  WORD    magenta;
  WORD    yellow;
  WORD    black;
};

typedef enum {
    COLOR_GRAY       =   1,
    COLOR_RGB,
    COLOR_XYZ,
    COLOR_Yxy,
    COLOR_Lab,
    COLOR_3_CHANNEL,        // WORD per channel
    COLOR_CMYK,
    COLOR_5_CHANNEL,        // BYTE per channel
    COLOR_6_CHANNEL,        //      - do -
    COLOR_7_CHANNEL,        //      - do -
    COLOR_8_CHANNEL,        //      - do -
    COLOR_NAMED,
} COLORTYPE;

From: Antti Nivala (antti.nivala@motivesys.com)
Subject: Re: Transforming colors with ICM 
Date: 2004-01-06 05:04:42 PST 
...............
...............
..............

N>        Testing profile 'Photoshop4DefaultCMYK.icc'
N>                RGB(FFFF, FFFF, FFFF) aka 'White' corresponds to CMYK(  10,    A,    0,    0)
N>                RGB(FFFF,    0,    0) aka 'Red'   corresponds to CMYK(   0, EB3C, FF5C,    0)
N>                RGB(   0, FFFF,    0) aka 'Green' corresponds to CMYK(A5D1,    0, EE2A,    0)
N>                RGB(   0,    0, FFFF) aka 'Blue'  corresponds to CMYK(FFFF, DABE,    0,    0)
N>

A>...
A>

A>typedef enum {
A>    COLOR_GRAY       =   1,
A>    COLOR_RGB,
A>    COLOR_XYZ,
A>    COLOR_Yxy,
A>    COLOR_Lab,
A>    COLOR_3_CHANNEL,        // WORD per channel
A>    COLOR_CMYK,
A>    COLOR_5_CHANNEL,        // BYTE per channel
A>    COLOR_6_CHANNEL,        //      - do -
A>    COLOR_7_CHANNEL,        //      - do -
A>    COLOR_8_CHANNEL,        //      - do -
A>    COLOR_NAMED,
A>} COLORTYPE;
A>

TranslateBitmapBits reports an error in a similar situation, I don't understand why TranslateColors does not.

using System;
using System.Runtime.InteropServices;

namespace ICM
{
    public class Program
    {
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        struct DISPLAY_DEVICEW
        {
            public int Size;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 32)]
            public string DeviceName;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
            public string DeviceString;
            public int StateFlags;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
            public string DeviceID;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 128)]
            public string DeviceKey;
        }

        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        struct PROFILEW
        {
            public int Type;
            [MarshalAs(UnmanagedType.BStr)]
            public string Data;
            public int DataSize;
            
            public PROFILEW(string filename)
            {
                Type = 1;
                Data = filename;
                DataSize = 2 * filename.Length;
            }
        }

        struct CIEXYZ
        {
            public int ciexyzX;
            public int ciexyzY;
            public int ciexyzZ;
        }

        struct CIEXYZTRIPLE
        {
            public CIEXYZ ciexyzRed;
            public CIEXYZ ciexyzGreen;
            public CIEXYZ ciexyzBlue;
        }
        
        [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
        struct LOGCOLORSPACEW
        {
            public int lcsSignature; 
            public int lcsVersion; 
            public int lcsSize;
            public int lcsCSType;
            public int lcsIntent; 
            public CIEXYZTRIPLE lcsEndpoints;
            public int lcsGammaRed;
            public int lcsGammaGreen; 
            public int lcsGammaBlue;
            [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
            public string lcsFilename;
        }; 

        struct ColorType
        {
            public const int COLOR_GRAY = 1;
            public const int COLOR_RGB = 2;
            public const int COLOR_XYZ = 3;
            public const int COLOR_Yxy = 4;
            public const int COLOR_Lab = 5;
            public const int COLOR_3_CHANNEL = 6;
            public const int COLOR_CMYK = 7;
            public const int COLOR_5_CHANNEL = 8;
            public const int COLOR_6_CHANNEL = 9;
            public const int COLOR_7_CHANNEL = 10;
            public const int COLOR_8_CHANNEL = 11;
            public const int COLOR_NAMED = 12;
        }

        [StructLayout(LayoutKind.Sequential)]
        struct RGBCOLOR
        {
            public short Red;
            public short Green;
            public short Blue;
        }

        [StructLayout(LayoutKind.Sequential)]
        struct CMYKCOLOR
        {
            public short Cyan;
            public short Magenta;
            public short Yellow;
            public short Black;
        }

        [DllImport("User32.dll")]
        static extern bool EnumDisplayDevicesW(string device, int deviceIndex, ref DISPLAY_DEVICEW displayDevice, uint flags);
        
        [DllImport("Gdi32.dll")]
        static extern IntPtr CreateDC(string driver, string device, IntPtr reserved, IntPtr printerData);

        [DllImport("Gdi32.dll")]
        static extern bool DeleteDC(IntPtr hDC);

        delegate int EnumICMProfilesCallback(string filename, int lParam);
        
        [DllImport("Gdi32.dll")]
        static extern int EnumICMProfiles(IntPtr hDC, EnumICMProfilesCallback lpEnumFunc, int lParam);

        [DllImport("mscms.dll")]
        static extern IntPtr OpenColorProfileW(ref PROFILEW profile, int access, int shareMode, int creationMode);

        [DllImport("mscms.dll")]
        static extern bool CloseColorProfile(IntPtr hProfile);

        [DllImport("mscms.dll")]
        static extern IntPtr CreateColorTransformW(ref LOGCOLORSPACEW logColorSpace, IntPtr hProfileDestination, IntPtr hProfileSource, int flags);

        [DllImport("mscms.dll")]
        static extern bool DeleteColorTransform(IntPtr hColorTransform);

        [DllImport("mscms.dll")]
        static extern bool TranslateColors(
            IntPtr hColorTransform,
            [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)][In] RGBCOLOR[] inputColor, int inputColorCount, int MustBe2,
            [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)][Out] CMYKCOLOR[] outputColor, int MustBe7);
        [DllImport("mscms.dll")]
        static extern bool TranslateColors(
            IntPtr hColorTransform,
            [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)][In] CMYKCOLOR[] inputColor, int inputColorCount, int MustBe7,
            [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)][Out] RGBCOLOR[] outputColor, int MustBe2);

        static void WriteTransform(IntPtr hColorTransform, short r, short g, short b)
        {
            RGBCOLOR[] inColor = new RGBCOLOR[1];
                    
            inColor[0].Red = r;
            inColor[0].Green = g;
            inColor[0].Blue = b;

            CMYKCOLOR[] outColor = new CMYKCOLOR[inColor.Length];

            if (TranslateColors(hColorTransform, inColor, inColor.Length, 2, outColor, 7))
            {
                Console.WriteLine(
                    "\t\tRGB({0}, {1}, {2}) = CMYK ({3}, {4}, {5}, {6})",
                    inColor[0].Red, inColor[0].Green, inColor[0].Blue,
                    outColor[0].Cyan, outColor[0].Magenta, outColor[0].Yellow, outColor[0].Black);
            }    
        }
        
        static int EnumICMProfilesProc(string filename, int lParam)
        {
            Console.WriteLine("\tProfile: {0}", filename);
            
            PROFILEW profile = new PROFILEW(filename);

            IntPtr hProfile = OpenColorProfileW(ref profile, 1 /* PROFILE_READ */, 0x00000007 /* FILE_SHARE_ALL */, 3 /* OPEN_EXISTING */);

            if (hProfile != IntPtr.Zero)
            {
                LOGCOLORSPACEW logColorSpace = new LOGCOLORSPACEW();

                logColorSpace.lcsSignature = 0x50534F43; /* LCS_SIGNATURE */
                logColorSpace.lcsIntent = 0x00000004; /* LCS_GM_IMAGES */
                logColorSpace.lcsVersion = 0x0400;
                logColorSpace.lcsSize = Marshal.SizeOf(logColorSpace);
                logColorSpace.lcsCSType = 0x57696E20; /* LCS_WINDOWS_COLOR_SPACE */

                IntPtr hColorTransform = CreateColorTransformW(ref logColorSpace, hProfile, IntPtr.Zero, 0x00000003 /* BEST_MODE */);

                if (hColorTransform != IntPtr.Zero)
                {
                    WriteTransform(hColorTransform, 255, 0, 0);
                    WriteTransform(hColorTransform, 0, 255, 0);
                    WriteTransform(hColorTransform, 0, 0, 255);
                    
                    DeleteColorTransform(hColorTransform);
                }
                
                CloseColorProfile(hProfile);
            }
            
            return 1;
        }
        
        static void Main(string[] args)
        {
            for (int deviceIndex = 0; deviceIndex < 10; ++deviceIndex)
            {
                DISPLAY_DEVICEW displayDevice = new DISPLAY_DEVICEW();
                
                displayDevice.Size = Marshal.SizeOf(displayDevice);

                if (EnumDisplayDevicesW(null, deviceIndex, ref displayDevice, 0))
                {
                    Console.WriteLine("Device: {0}", displayDevice.DeviceName);
                    
                    IntPtr hDC = CreateDC(displayDevice.DeviceName, null, IntPtr.Zero, IntPtr.Zero);
                    
                    EnumICMProfiles(hDC, new EnumICMProfilesCallback(EnumICMProfilesProc), 0);
                    
                    DeleteDC(hDC);

                    Console.WriteLine();
                }
            }
        }
    }
}